Preheat oven to 325 degrees.
Chop pecans and place them on a baking sheet. Bake on 325 for 10 minutes, stirring pecans every 2-3 minutes. When finished, set aside to cool while you work on the peaches and batter.
Raise the oven temperature to 350 degrees.
If using fresh peaches, blanch the peaches by boiling them in water for 4 minutes, then moving to a bowl of ice water. Let them cool for a few minutes before removing from the ice water and removing the seeds, skins, and slicing the peaches. If using frozen peaches, skip to the next step.
Place the peaches in a bowl, add the granulated sugar and lemon juice. Stir to combine, then set aside for 5 minutes.
After 5 minutes, strain the juice from the peaches and add the peaches to a 10x15 casserole dish.
In a large mixing bowl, combine softened butter, brown sugar, eggs, pumpkin puree, and sour cream, mixing well with a spoon or whisk.
In a smaller bowl, combine flour, baking powder, baking soda, cinnamon, ginger, nutmeg, and salt, mixing well.
Add dry ingredients to wet ingredients, mixing well. Batter will be thick.
In a small bowl, make the streusel by combining flour, brown sugar, cinnamon, and butter. Using your thumbs, pinch the butter into the other ingredients, mixing it all thoroughly.
Once cooled, add pecans to streusel mixture. Mix it all together really well.
Sprinkle half the streusel over the peaches.
Spoon dollops of the cake batter onto the peaches. Distributing the dollops will help to smooth the batter easier.
When all the batter is spooned onto the peaches, carefully spread and smooth out the batter over the peaches.
Sprinkle the other half of the streusel on top of the cake batter, distributing as evenly as possible.
Bake on 350 for 50 minutes, or until a toothpick inserted comes out mostly clean. The peaches will leave some residue on the toothpick, but there shouldn't be any crumbs from the cake on the toothpick.
Enjoy warm with a scoop of vanilla ice cream(or 3)!
